Illuminating structure.



110.721,256.' l PATBNTED 333.2519031 I ILLUMINATING STRUCTURE.

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UNITED STATES APATENT OEEICE.

FRANK L. O. W'ADSWORTI-I, OF WILLIAMS BAY, WISCONSIN, ASSIGNOR, BY IWIESNE ASSIGNMENTS, TO PRESSED PRISM PLATE GLASS OOIWIPANY, A CORPORATION OF WEST VIRGINIA.

ILLUMINATINGiSTRUCTURE.

SPECIFICATION forming part of Letters Patent N o. 721,256, dated February 24, 1903.

Application filed April 13, 1898. Serial No. 677,487. (No model.)

To @ZZ whom, t may concern.-

Be it known that I, FRANK L. O. WADS- WORTH, a citizen of the United States, residing at Williams Bay, in the county of l/Valworth and State of IVisconsin, have invented certain new and useful Improvements in Illuminating Structures, of which the following is a specification.

My invention relates to illuminating strucro tures in which prisms are employed; and my improvement consists inproviding the structures with prisms having inwardly-projecting parts with upper reflecting-faces and in constructing the same as fully set forth hereinafter and as illustrated in the accompanying drawings, in which- Figure l is a cross-section of part of an illuminating-panel embodying my invention. Fig. 2 is a sectional View illustrating a dierzo ent form of prism-bars embodying my improvement.

In prismatic plates of the usual construction a large part of the light which falls upon the first face and is directed by refractionv z 5 through said prismatic block will fall upon the surface of the prism just below that through which it first passes and will by this second prism be refracted downward in the reverse direction to that in which it was re- 3o fracted in the iirstprism and emerge from the second prism in a reverse downward direction. Part of this light will fall downward past the point of the third prism and fall on the floor at the foot of the window.

Another part will fall upon the face of the third prism, be refracted and reflected again at the face of this prism, and will finally pass out of the structure at the same face at which it originally entered, so that in such struc- 4o tures only about forty per cent. of the incident light coming from an upward direction will be directed into the room in the direction availableforilluminatingpurposes. Thisloss may be avoided by constructing the prismfaces differently;but a simpler method of avoidingloss, retaining the old forms of prismplates, consists in applying a coating of silver or other suitable material to the faces, so as to form external reflecting-faces which will 5o reflect the rays falling upon them in an upvupward toward the ceiling, as at lb 2b.

ward direction toward the ceiling of the room. In any case it is very much better that the light-rays shall fall upon the ceiling, from whence they will be diffused uniformly over y a room, than that they should fall upon the floor at the foot of the window, where underordinary circumstances theirilluminating effect is practically zero, and where the ceiling is provided with or coated to constitute a reflector the upward projection of the light- 6o rays is essential to the best results.

While the old forms of structures may be provided with reIiecting-faces, as described, I have devised an improved form especially adapted to utilize such reflecting-faces to the best advantage. As shown in Fig. l, the prism-plate has a series of prisms P P, each with a curved upper reflecting-face s, a flat face s2, and an inclined face u. The upper reflecting-faces s of the prisms are shaped in 7o such a way that the light falling upon them after refraction through the main body of the prism-plate is directed inward into the room inv nearly horizontal lines instead of upward toward the ceiling. The form of surface which is best adapted to secure this result is a surface whose cross-section corresponds to in front of the receiving-surface. Rays, such as l 2, which pass through the main body of 8o the prism-plate emerge at the face u, and falling. upon the silvered surface s will then be reflected therefrom, either horizontally into the room, as at la 2a ta, or be directed slightly The 8o main body of the prism-plate may be so shaped that it vwill direct the more nearly horizontal rays, as 3, into the room horizontally by refraction alone at the faces u, as at 3a 3% Thus nearly the whole body of rays falling upon 9o the outer surface t of this prismatic reflectorplate will be directed into the room nearly horizontally, either by combined refraction through the body of the prism-plate and-thev subsequent reilection on the faces s'or by the 95 refraction alone.

In an illuminating structure the separate prism elements may be made in one piece, as shown, or of independent parts or bars placed together one above the otherfor instance, of roo separatefbars of the shapes shown in Fig. 2. In many cases it is desirable to Yplace a glass plate B back of the prism-plate, so as to protect the thin projection portions of the latter, or the thin projecting parts may be made of sheet metal integral with the part forming 2. A prismatic illuminating structure havl ing a at receiving-surface and at the oppoi site side a series of curved opaque externallyreecting faces s each coinciding with a part Yof a parabolic curve and below each face s Vtwo faces u s2 meeting at an obtuse rentrant angle, Vsubstzmtially as set forth.

3. An illuminator prism-bar consisting of a prismatic body of transparent material and a reflecting-plate applied to one of the faces of the body and projecting beyond the same, substantially as set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

F. L. O. WADSWORTH.

Witnesses:

HARRY E. HAY, W. CLARENCE DUVALL. 

